Field of the Invention
The present invention relates to an image reading apparatus reading image information from a sheet such as a document and to an image forming apparatus including the same.
Description of the Related Art
Hitherto, there is known an image reading apparatus including a document feeding apparatus (referred to as an ‘ADF’ (Auto Document Feeder) hereinafter) such as a double-sided auto document feeder for use in an image forming apparatus such as a digital copier. The image reading apparatus including the ADF of this sort is configured to move an image reading portion provided in a scanner unit under the ADF by a motor to scan a document while conveying the document between a platen roller within the ADF and a document flow-reading glass, and to detect a reflection light thereof by the image reading portion in copying the document within the ADF. Then, the image forming apparatus is configured to obtain a copy image by performing an image forming process in an image forming portion based on data thus detected.
By the way, there is known an image reading apparatus including image reading portions disposed on the ADF side and on the scanner unit side so as to face with each other to read both sides of the document being conveyed simultaneously (consecutively) as disclosed in Japanese Patent No. 4869409 for example. In the image reading apparatus disclosed in Japanese Patent No. 4869409, first and second reading guide portions are disposed at first and second reading positions, respectively, so as to face with each other to suppress defocus from being generated. Then, these first and second reading guide portions are configured to be able to change a gap between them, i.e., to be able to change a gap forming a document conveyance path at the first and second reading positions.
However, the first reading guide portion is provided on the scanner unit side and the second reading guide portion is provided on the ADF side in the image reading apparatus reading the both surfaces of the document simultaneously as disclosed in Japanese Patent No. 4869409. The ADF is provided openably with respect to the scanner unit, and it is difficult to keep a distance of the gap of the document conveyance path favorably at the first and second reading positions in a state in which the ADF is closed with respect to the scanner unit if a relative positional displacement exists between the ADF and the scanner unit. Therefore, if the ADF is displaced relatively from the scanner unit, it is difficult to keep the gap at the both reading positions favorably also in the image reading apparatus disclosed in Japanese Patent No. 4869409. That is, even if an adjustment is made so that the gap at the first reading position becomes favorable in the state in which the ADF is closed with respect to the scanner unit, there is a problem that it is hard to keep the gap composing the document conveyance path at the second reading position favorable due the allowance and others.